The scroll-type fluid machine forms a working gas chamber by combined paired fixed scroll member and revolving scroll member, which are formed by vertically mounting spiral wraps on end plates, with their phases shifted. With such a scroll-type fluid machine, the gas pressure in the working gas chamber acts in a direction to separate the fixed scroll member and the revolving scroll member. In this way, the distance between the tips of the spiral wraps increases, causing gas leakage. As a countermeasure, a back-pressure chamber in which high-pressure gas is introduced is partitioned at the back side of the revolving scroll member, and the revolving scroll member is pushed toward the fixed scroll member by the gas pressure. It is known that, by doing so, gas leakage can be decreased, and high efficiency can be achieved.
To form the back-pressure chamber on the back side of the revolving scroll member, the back-pressure chamber must be partitioned and sealed off from the surroundings. Such a sealing structure proposed in Patent Document 1 has a configuration in which a groove is formed in a fixed support member supporting the back side of a revolving scroll member, a ring-shaped sealing member (back-pressure partitioning belt) and a spring member are installed in this groove, and the sealing member is pushed by the spring member toward the revolving scroll member. However, when such a sealing member is used, it is necessary that the sealing member be provided with a divided surface. Therefore, gas leakage from the divided surface is a serious problem.
Patent Document 2 proposes using a sealing member in which a so-called annular U sealing member, which has a sliding surface on one side in contact with a revolving scroll member and which has a angular-U-shaped cross-section, is installed horizontally (in a direction parallel to the sliding direction of the revolving scroll member) such that its opening faces a back-pressure chamber and such that the sliding surface is pushed against the revolving scroll member by an internal pre-load spring of the annular U sealing member.
Patent Document 1:
Japanese Unexamined Patent Application, Publication No. HEI-08-61258
Patent Document 2:
Japanese Unexamined Patent Application, Publication No. 2002-54583